Yuichi Ambe

Quadrupedal bounding with spring-damper body joint

Stable locomotion indicates a stable limit cycle generated in the dynamic system. Although quadrupedal bound gait models have been investigated, there is no research which shows the generation of limit cycle and its dynamic properties. In the present study, we analyze a quadrupedal bound gait model which goes down slope and has back and front bodies with spring-damper joint between the bodies. We found the periodic bound gait which achieves a stable limit cycle and convergence property against perturbations.

Adaptive neural oscillators with synaptic plasticity for locomotion control of a snake-like robot with screw-drive mechanism

Central pattern generators (CPGs) play a crucial role for animal locomotion control. They can be entrained by sensory feedback to induce proper rhythmic patterns and even store the entrained patterns through connection weights. Inspired by this biological finding, we use four adaptive neural oscillators with synaptic plasticity as CPGs for locomotion control of our real snake-like robot with screw-drive mechanism. Each oscillator consists of only three neurons and uses adaptive mechanisms based on frequency adaptation and Hebbian-type learning rules. It autonomously generates proper periodic patterns for the robot locomotion and can be entrained by sensory feedback to memorize the patterns. The adaptive CPG system in conjunction with a simple control strategy enables the robot to perform self-tuning behavior which is robust against short-time perturbations. The generated behavior is also energy efficient. In addition, the robot can also cope with corners as well as move through a complex environment with obstacles.

Stability analysis of a hexapod robot driven by distributed nonlinear oscillators with a phase modulation mechanism

In this paper, we investigated the dynamics of a hexapod robot model whose legs are driven by nonlinear oscillators with a phase modulation mechanism including phase resetting and inhibition. This mechanism changes the oscillation period of the oscillator depending solely on the timing of the foots contact. This strategy is based on observation of animals. The performance of the controller is evaluated using a physical simulation environment. Our simulation results show that the robot produces some stable gaits depending on the locomotion speed due to the phase modulation mechanism, which are simillar to the gaits of insects.

Leg-grope-walk — Walking strategy on weak and irregular slopes for a quadruped robot by force distribution

When a legged-robot walks on an irregular terrain such as a damaged area, some footholds may collapse due to the external force caused by the walking robot, and consequently the robot will stumble and fall. We have earlier proposed a locomotion method in which the quadruped robot does not stumble and cause a large collapse of the surrounding area on a weak horizontal plane. In this paper, we extend this method to weak and irregular slopes. In the case of slopes, we should consider “slippage”. We propose a force distribution method for the leg-grope that also considers slippage. To demonstrate the effectiveness of proposed method, we will show an experimental result.

Low latency and high quality two-stage human-voice-enhancement system for a hose-shaped rescue robot

2-1-2 Hitotsubashi, Chiyoda-ku, Tokyo 101-8430, Japan ∗4Graduate School of Systems and Information Engineering, Tsukuba University 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan ∗5Department of Informatics, School of Multidisciplinary Sciences, SOKENDAI 2-1-2 Hitotsubashi, Chiyoda-ku, Tokyo 101-8430, Japan ∗6Graduate School of Information Science, Tohoku University 6-6-01 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579, Japan ∗7Graduate Program for Embodiment Informatics, Waseda University 2-4-12 Okubo, Shinjuku, Tokyo 169-0072, Japan

Adaptive Control Strategies for Interlimb Coordination in Legged Robots: A Review

Walking animals produce adaptive interlimb coordination during locomotion in accordance with their situation. Interlimb coordination is generated through the dynamic interactions of the neural system, the musculoskeletal system, and the environment, although the underlying mechanisms remain unclear. Recently, investigations of the adaptation mechanisms of living beings have attracted attention, and bio-inspired control systems based on neurophysiological findings regarding sensorimotor interactions are being developed for legged robots. In this review, we introduce adaptive interlimb coordination for legged robots induced by various factors (locomotion speed, environmental situation, body properties, and task). In addition, we show characteristic properties of adaptive interlimb coordination, such as gait hysteresis and different time-scale adaptations. We also discuss the underlying mechanisms and control strategies to achieve adaptive interlimb coordination and the design principle for the control system of legged robots.

Body flexibility effects on foot loading based on quadruped bounding models

In this paper, we investigate effects of the flexibility of the body on locomotion of a quadruped robot using computer simulation with physical models. So far, many researchers have used legged robots whose bodies consist of one rigid body and examined dynamical properties, such as stability of gaits and energy efficiency. However, from the observation of animals, it has been suggested that flexibility of the body is important for dynamic locomotion. We used two types of simple physical models, with and without a springy joint in their body to evaluate the importance of the body flexibility on the bounding gait, where left and right legs simultaneously kick the ground. Our simulation results show that when we use the same mechanical energy for these two models, the maximum ground reaction force for the model with a body springy joint is smaller than that for the model without a body springy joint (rigid body) even when their locomotion speeds are identical. This suggests that the flexibility of the body can reduce the foot loading of the robot in the bounding gait.

Development of a maneuverable flexible manipulator for minimally invasive surgery with varied stiffness

Complications in and post conventional invasive procedures makes minimal invasive surgery well accepted in society. It causes less pain and scarring, faster recovery, and reduces operative trauma for patients. To overcome the difficulties of limited steerability and stiffness control of conventional scope, a continuously curving manipulator actuated by smart material named shape memory alloys (SMA) is proposed in this paper. The segmented scope consisted of a compression spring backbone and three SMA actuators to dynamically control the shape of each segment of the manipulator as and when required. A detailed study was carried out to simulate the constraints of the manipulator and fit it to a given random curve in a 3-dimensional (3D) space in the best possible way. The paper also includes testing of one segment of the prototype with bending angles and force produced during actuation. Actuation time and cooling time, which is issue using SMA practically, are also discussed briefly. The manipulator seems to be a promising device to be able to follow given random complex 3D trajectories and vary segment stiffness as and when required.

Aerial Hose Type Robot by Water Jet for Fire Fighting

Disaster response, especially fire-fighting and rescue, is highly risky for firefighters engaged in action. As a result, many robots intended for fire-fighting have been proposed. However, it is difficult for them to directly access fire sources because their mobility is limited. Specifically, existing robots are large and heavy. Therefore, we propose a novel hose-type robot, which can fly directly into the fire source via a water jet. First, to control the reaction force for stable flying, we developed a nozzle module. By combining two nozzles whose outlet direction can be controlled, the resultant reaction force can be controlled. Finally, we developed a robot with a nozzle module and conducted an experiment. The experiment demonstrates that a robot with a length of approximately 2 m can fly stably in the air by leveraging the water jet. In addition, the head direction can also be controlled.

Simple analytical model reveals the functional role of embodied sensorimotor interaction in hexapod gaits

Insects have various gaits with specific characteristics and can change their gaits smoothly in accordance with their speed. These gaits emerge from the embodied sensorimotor interactions that occur between the insect’s neural control and body dynamic systems through sensory feedback. Sensory feedback plays a critical role in coordinated movements such as locomotion, particularly in stick insects. While many previously developed insect models can generate different insect gaits, the functional role of embodied sensorimotor interactions in the interlimb coordination of insects remains unclear because of their complexity. In this study, we propose a simple physical model that is amenable to mathematical analysis to explain the functional role of these interactions clearly. We focus on a foot contact sensory feedback called phase resetting, which regulates leg retraction timing based on touchdown information. First, we used a hexapod robot to determine whether the distributed decoupled oscillators used for legs with the sensory feedback generate insect-like gaits through embodied sensorimotor interactions. The robot generated two different gaits and one had similar characteristics to insect gaits. Next, we proposed the simple model as a minimal model that allowed us to analyze and explain the gait mechanism through the embodied sensorimotor interactions. The simple model consists of a rigid body with massless springs acting as legs, where the legs are controlled using oscillator phases with phase resetting, and the governed equations are reduced such that they can be explained using only the oscillator phases with some approximations. This simplicity leads to analytical solutions for the hexapod gaits via perturbation analysis, despite the complexity of the embodied sensorimotor interactions. This is the first study to provide an analytical model for insect gaits under these interaction conditions. Our results clarified how this specific foot contact sensory feedback contributes to generation of insect-like ipsilateral interlimb coordination during hexapod locomotion.